1. Field of the Present Invention
The present invention relates to a method and apparatus to determine asset location by calculating the relative position of a plurality of GPS enabled devices transported together. More particularly, the present invention derives the most accurate GPS position data to create a real time location system to find the exact location of a single box.
2. Description of Related Art
In automotive GPS receivers, metallic features in windshields, such as defrosters or car window tinting films, can act as a Faraday cage, degrading reception inside the car. Man-made electromagnetic interference (EMI) can also disrupt or GPS signals. In one well-documented case it was impossible to receive GPS signals in the entire harbor of Moss Landing, Calif. due to unintentional jamming caused by malfunctioning TV antenna preamplifiers. Intentional jamming is also possible. Generally, stronger signals can interfere with GPS receivers when they are within radio range or line of sight.
In 2002, a detailed description of how to build a short-range GPS L1 C/A jammer was published in the online magazine. The U.S. government believes that such jammers were used occasionally during the 2001 war in Afghanistan, and the U.S. military claims to have destroyed six GPS jammers during the Iraq War, including one that was destroyed with a GPS-guided bomb. A GPS jammer is relatively easy to detect and locate, making it an attractive target for anti-radiation missiles.
Some countries allow GPS repeaters to facilitate the reception of GPS signals indoors and in obscured locations; however, under European Union and U.K. laws, these are prohibited because the signals can interfere with other GPS receivers that receive data from both satellites and the repeater.
Various techniques can address interference. One is to not rely on GPS as a sole source. According to John Ruley, “IFR pilots should have a fallback plan in case of a GPS malfunction” Receiver Autonomous Integrity Monitoring (RAIM) is included in some receivers, to warn if jamming or another problem is detected. The U.S. military has also deployed since 2004 their Selective Availability/Anti-Spoofing Module (SAASM) in the Defense Advanced GPS Receiver (DAGR). DAGR detects jamming and maintains its lock on encrypted GPS signals during interference.
Real time location systems improve how companies locate, track, and manage high value assets. Modern asset management requires tracking the location of containers and cargo. Currently, various types of Real Time Location Systems (RTLS) such as ISO/IEC 24730-2, Cisco, CCX Wi-Fi, precision GPS and Ultra-Wideband are being used to fit the operational needs of the customer.
The present application discloses a method and apparatus designed to increase reliability location data by creating a GPS mesh network device to communicate with existing GPS devices and coordinate data to improve visibility into the exact location and status of assets. This increased visibility will enable the customer to pinpoint the real time location of a single box more accurately and efficiently than the prior art. This level of real time asset management translates into greater operational efficiency and performance, cost reductions, and improved safety and security.